Simulation of particle trajectories in a vortex-induced flow: application to seed-dependent flow measurement techniques

The trajectories of heavy particles (rho(particle)/rho(fluid) much greater than 1) are simulated in a two-dimensional free vortex flow. The results show that heavy particles, even with small diameters, cannot properly trace the fluid and develop a centrifugal motion. This behaviour leads to a rapid depletion of particles in the vortex core, which, in seed-dependent measurements such as particle image velocimetry (PIV) or laser Doppler velocimetry, produces a marked increase in measurement errors. Some examples are given and the evolution of the local concentration of particles is simulated. Synthetic images have been generated using the information about its motion in a two-dimensional free vortex flow. A wing-tip vortex is simulated, showing good agreement with experimental results present in the literature. Standard PIV measurements have been performed over the synthetic images, showing the effect of core depletion of particles on the incidence of erroneous measurements.